The proteoglycans of human cementum: immunohistochemical localization in healthy, periodontally involved and ageing teeth

Cementum is believed to play a regulatory role in periodontal regeneration through a variety of macromolecules present in its extracellular matrix (ECM), among which are the proteoglycans (PG). The PG of human cementum have not been fully characterized. This study has used a standard indirect immunoperoxidase technique to investigate the presence and distribution of PG species within the ECM of human cementum. Freshly extracted human permanent teeth were separated into 8 age groups; each group was subdivided to include healthy and periodontally involved teeth, which were then fixed, demineralized and wax-embedded. Sections were incubated with polyclonal antibodies recognizing protein core epitopes in the large chondroitin sulphate PG versican and the small interstitial PG decorin, biglycan, fibromodulin and lumican. Immunoreactivity to versican, decorin, biglycan and lumican was evident at the borders and lumina of a proportion of lacunae and canaliculi surrounding cementocytes in cellular cementum, as well as on inserted periodontal ligament (PDL) fibres. Biglycan was also present along incremental lines in cellular cementum, whereas staining for fibromodulin was negative. In acellular cementum, no immunoreactivity was evident with any of the antibodies used except on inserted PDL fibres. These results indicate that versican, decorin, biglycan and lumican are components of the ECM of cellular, but not of acellular cementum. Neither age nor periodontal diseases appear to qualitatively influence the PG population of cementum. The distribution of PG epitopes around a proportion of cementocytes suggests the existence of different cementocyte subpopulations, or a differential response of these cells to yet undefined stimuli.